Embolic compositions can be used to prevent or to treat certain conditions in the body. For example, in therapeutic vascular occlusions (sometimes called “embolizations”), particulate embolic compositions can be used to block, or occlude, vessels in the body. The embolic compositions can be used to block microvascular supplies of blood to tumors (thereby depriving the tumors of resources to grow), or to block hemorrhagic conditions in the body (thereby reducing or stopping bleeding). The compositions can be delivered to a target site using a catheter that has been introduced into the vessel.